Fuzz Face

This is the Fuzz Face, the legendary fuzz distortion pedal. With this PCB you can build the original or many other variants using either Germanium or Silicon transistors.
Steps

Created by DHEA
Status: Active
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Designators and components Step 2 of 4

COMPONENT LIST

PCB
PCB  FUZZ FACE DIY PCB GUITAR EFFECT
Capacitors        
C1    2.2u    2.2UF 35V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM
C2    22u    22UF 50V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM
C3    10n    10NF 0.01UF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
C4    47u    47UF 25V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM NICHICON
Transistors        
Q1    PNP 2N3906 / NPN  2N3904BC108 or BC109
Q2    PNP 2N3906 / NPN  2N3904BC108 or BC109
Sockets     40 PIN DIP SIP IC SOCKETS ADAPTOR SOLDER TYPE
Resistors        
R1    100k  100K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R2    33k    33K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R3    470    470 OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R4    1M    100K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
Bias  50k     50K OHM TRIMMER POTENTIOMETER CERMET 1 TURN 3362P
Potentiometers        
FUZZ 1k-B         1K OHM LINEAR TAPER POTENTIOMETER
VOL    500k-A    500K OHM LOGARITHMIC TAPER POTENTIOMETER

CIRCUIT

PCB

NEGATIVE OR POSITIVE GROUND

The PCB is designed for the original positive ground version (PNP transistors). A positive ground pedal cannot be connected to the power supply in chain with your other pedals (negative ground).  It is necessary to use a 9V battery, an isolated power supply or a voltage inverter.

If you are planning to use germanium transistors, you should build the positive ground version since most of the germanium transistors are PNP (for example AC128). However, if you are going to use silicon transistors, you should build the NPN version... which will be more convenient to power up the circuit in chain with your other pedals.

TRANSISTORS

The original Fuzz Face uses germanium PNP transistors (AC128 or NKT275); You should use a low gain for Q1 (β=70-80) and a high gain for Q2 (β=110-130). Germanium transistors tend to have leakage current and a varying gain value. For the PNP silicon version, you can use 2N3906.

For NPN silicon version you can use 2N3904BC108 or BC109. You can use sockets and try different transistor combinations. To use to the negative ground version (NPN transistors): change to NPN transistors, flip the polarity of the electrolytic capacitors (C1, C2 and C4) and connect the +9V where it is marked -9V.

Capacitors for PNP version                 Capacitors for NPN version

      

For the correct position of the transistors, you can use the following figures.

 

In the following table find some transistors you can use. 

TRANSISTOR SOCKETS

It is recommended to use sockets for the transistors. You can use 3 pin headers (40 PIN DIP SIP IC SOCKETS ADAPTOR SOLDER TYPE) or transistor sockets.

 

BIASING THE CIRCUIT

Place the trimmer to bias the circuit. By using a voltmeter, you can measure the voltage over the "Bias" pad and adjust to half of the power supply. For example, if you are using a 9V power supply, the bias voltage should be 4.5V. Note that if you are using germanium transistors the biasing will be influenced by ambient conditions such as temperature. Other method is just using your ears, rotate the trimmer until you find the point you most like.